The Association between Weather and Contamination on Crops Prior to Harvest: A Mixed Models Analysis 公开

Abstract

Foodborne illness associated with produce is costly in terms of human health and economic losses. The need to improve food safety is increasing as demands on the global food supply are also increasing. However, the environmental conditions that influence the inoculation, proliferation, and diffusion of fecal contamination on produce are not well understood. Therefore, we aimed to assess an association between temperature or precipitation and fecal contamination on produce prior to harvest. Between 2000 and 2002, we assayed for three fecal indicators (APC, coliforms, or Enterococcus) on 10 different types of produce collected from 15 fields that were clustered in the southern U.S. Weather data was obtained from a single NOAA weather station within 100km of the fields. We used a mixed models approach to analyze the relationship between indicator concentrations on crops and weather over a week-long lag period prior to sample collection. Average daily temperature was significantly associated with indicator growth for five days prior to sample collection. On the other hand, daily total precipitation had a significant association with indicator concentrations for only one or two days prior to collection. Our results indicated that there is a significant association between weather and fecal indicator proliferation on crops in the field. Indicator concentrations may have increased as the temperature increased towards the optimal growing temperature for the bacteria. Precipitation may be creating moist conditions conducive to bacterial growth, spreading contamination onto the field, or washing contamination off of the plant. Therefore, new food safety policies that are weather dependent may be necessary to improve the safety of the global food supply.

Table of Contents

LITERATURE REVIEW - 1

Why Study Produce Contamination? - 1

What is Produce Contamination? - 1

Where Contamination Occurs - 2

Contamination on the Farm - 3

Indicators of Contamination - 3

Climate Effects on Plants and Pathogens - 6

Climate Models - 8

Clean Greens I study - 8

Goals and Aims - 9

Significance - 10

INTRODUCTION - 11

METHODS - 14

Produce and Indicator Data - 14

Weather Data - 14

Statistical Analysis - 15

RESULTS - 17

Figure 1: Location of sample collection - 20

Table 1: Sample distribution according to month and crop - 21

Table 2: Mean and SE for indicator concentrations for crop and field - 22

Figure 2: Association between precipitation and indicator concentrations - 23

Figure 3: Association between temperature and indicator concentrations - 24

Figure 4: Quadratic model fit between precipitation and indicator concentrations - 25

Figure 5: Quadratic model fit between temperature and indicator concentrations - 26

DISCUSSION - 27

PUBLIC HEALTH IMPLICATIONS AND RECOMMENDATIONS - 32

REFERENCES - 34

About this Master's Thesis

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School	Rollins School of Public Health
Department	Hubert Department of Global Health
Degree	MPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health
关键词	produce climate food safety
Committee Chair / Thesis Advisor	Leon, Juan, Emory University
Committee Members	Remais, Justin V, Emory University
Partnering Agencies	Emory University schools, faculty or affiliated programs

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